The biggest problem with CG explosions is that they don't interact with their environment and often look very fake. MarkG and rjschwarz are right, though: homemade explosives are definitely NOT the way to go. In fact, really anything that lights on fire and goes "bang" can be seriously dangerous if it's not being supervised by an experienced pyrotechnic--ESPECIALLY when there are people in frame with the explosion. Now, I've done some stupid, dangerous pyro effects in my day and let me tell you that they usually aren't even all that impressive--for one thing, when you see an explosion in a movie they're not blowing up an actual bomb--they've probably got some gas jets and other things rigged up, but even more important are the camera work, editing, and sound design. If you take the actual pyro element out of the equation and focus on communicating the IMPACT rather than the blast itself, you will probably end up with a better product in the long run, anyway.

-----------------
Andrew Gingerich
Exploding Goldfish Films
Check out my vodcast on iTunes: http://phobos.apple.com/WebObjects/MZStore.woa/wa/viewPodcast?id=96931870
and my blog at http://www.exgfilms.com

If you plan things out you can combine thrown dirt with a flash of light and a CGI explosion and make it look as if the CGI explosion tossed the dirt and created the light. If done right it can look good, if added in as an afterthought it can look terrible.

For example if you ever watch the movie THE DEAD HATE THE LIVING they have some CGI fire that doesn't cast any light on the actors. That alone makes it stand out as really fake. A bit of onset lights reflected off of crumpled and then straightened out aluminum foil could have created firelight illumination on the walls and actors that could have sold the CGI.

RJSchwarz
San Diego, CA

Yes, I'll do that. What is a good program for adding explosions through CGI though?

___________________________________
You can't keep 'em out, they're already in!

A good program I don't know, but almost any modern editing program will let you drop in a layer and allow this sort of thing to some extent. The other thing you can do with a lot of programs is export the frames that the explosion appears in and then add the explosion in frame by frame in photoshop. As long as the explosion doesn't last two long this won't take forever.

Another thing to remember is there are real explosions and movie explosions. You would be surprised at how anti-climactic a military explosion is without the extra fuel used to make a bright flame. Real blasts are mostly smoke, a pressure wave and shrapnel that you won't see on film, and a lot of dirt and noise. To make it you just need something to toss up a bit of dirt, add in maybe two frames of blast, and then sell it with audio and twitching actor.

One of the better military movies is FULL METAL JACKET. THey have a scene where the Marines are moving in towards the imperial captial behind a tank and a mortor hits not to far away. In a "typical" movie it was far away and nobody would have been in danger. The blast didn't have a lot of pizzaz, yet LT Shortround was hit by the shrapnel and fell to the ground twitching. No visible blood or anything. Spooky, sick, and very real looking. Probably fairly cheap (if you ignore the tank and destroyed city that is).

RJSchwarz
San Diego, CA

Don't use cgi tools to do particle effects for things such as dirt, smoke, fire, water and so on, these look fake and takes years of experience to even get close to anything that looks good. Your best bet is to go stock footage and apply it over the footage you have, you can find a huge selection of free stock footage here : www.detonationfilms.com

Here they have smoke, blood, dust, dirt, shell blasts, shell ejections. The list is endless, keep in mind if your footage is already shot this may not match what you have in mind, but if your shoot is yet to come pre plan some of your shots, without a doubt the best free stock footage is here, if you want better stuff you'll pay ?80+ per 5 sec clip, if your willing to pay try : www.artbeats.com

The other option is to actually film your own stock footage against a black sheet/background and key it in. The possibilites are endless, but don't use CG effects there just not good enough for this type of work, CG is best used for stunt doubles or long distance shots, again you have to note your camera setting to match these in with your 3d program, note things like shutter speed, F-stop, distance and hieght from subject, also capture HDR shots for lighting if possible. CG is alot more work than it sounds, and believe me the results are never that great, you also need a huge processor and memory for rendering unless your shipping the files to a render farm. The choice is yours.

Yes, detonationfilms.com is a very good site for CGI effects. Do you know of a good program that I can add these to film with though?

___________________________________
You can't keep 'em out, they're already in!

Detonation Films dosn't supply CG effects, the effects in detonation films is called stock footage. There are a few promgrammes out there that allow you to key such footage, Premiere Pro, After Effects and VisionLab.

VisionLab can be purchased at www.FXhome.com This is the only place it can be purchased and is a great programme fr the price. The site also contains all the information about the effects your after, there are some step by step tutes on how to achive perfect results.

Good Luck with your project.

All the Best
Ash

OK, thank you. Do you know how I could get heaps of soil to fly up in the air without the use of CGI though?

___________________________________
You can't keep 'em out, they're already in!

quote:

---

Originally posted by Svelter

OK, thank you. Do you know how I could get heaps of soil to fly up in the air without the use of CGI though?

---

Air. Fill a tube (called a mortar) with debris, attach the other end to an air compressor and fire!

=============================================
The aim of an argument or discussion should not be victory, but progress.
Joseph Joubert, essayist (1754-1824)

Oh, that's fantastic! Thank you. But how do I get the air compressor to fire?

___________________________________
You can't keep 'em out, they're already in!

If you buy an insecticide sprayer of the pump variety you manually pump up the pressure. When the pressure valve is released it fires all of the air at once. This can send a small amount of fake blood or dirt flying away at a cost of less than $20.

If you want more flying dirt you can buy an air compressor which does the same thing but has an engine to build up the pressure so you can fill car tires and such with it. Cost if higher.

RJSchwarz
San Diego, CA

RJ is correct. For a lot of heavy debris like dirt you're going to need a fairly large air compressor. Here in the States they are easily and cheaply rented from building supply places. You "fire" it by simply opening the release valve - the compressed air escapes quickly, blowing all the debris out of the mortar.